Metal plating is a common art. Plating is used to add metal to worn parts, to coat a metal with another metal and for other purposes as well. In many cases, the metal to be plated is placed directly into the plating solution so that its entire surface can be plated. Often, however, people desire to plate only portions of the metal workpiece. To prevent undesired plating, a mask is applied to the workpiece in the areas not to be plated. Typically, this mask is in the form of a liquid that is brushed onto the metal as desired and allowed to dry. Once dry, the mask creates a barrier to the plating metal. When the plating process is complete, the mask can be removed, and the metal is then ready for use.
The liquid mask method does a good job. However, it is labor intensive. Also, because the mask is applied by hand, it is not always applied uniformly from piece to piece. To overcome these problems, reusable masks have been developed. An example of such a mask is found in U.S. Pat. No. 3,527,679 to Barile. The Barile patent teaches use of a soft reusable mask for plating machine parts. The plating builds up metal on areas of the part that have worn down. The Barile mask uses a mold to form a rubberized type mask. The mask is split to allow it to be placed over individual parts. Barile also teaches cutting out portions of the mask as needed, to expose other parts of the piece to be plated. To use the mask, the mask is split and placed around the metal part. The mask is secured using a rubber band. The metal can then be plated. After the plating, the mask can be removed to be used again on the next part.
U.S. Pat. Nos. 4,294,681 and 4,126,521 also teach mask forms. U.S. Pat. No. 4,294,681 teaches a mask that has a series of regular openings formed therein. This process begins by making a mask blank. The mask blank is then placed in a mold. Polyurethane is then placed in the mold over the blank. The polyurethane is then cured and treated. The mask is then removed from the mold ready to use. This mask has more durability than the rubber masks described above. U.S. Pat. No. 4,126,521 teaches using a mask of non-porous elastic material that is formed to cover the portions of metal that are not plated. The mask is held in a carrier that applies pressure to the mask thereby forming a liquid tight seal between the carrier and the article being plated. This design also has an electrode that extends through the mask where it contacts the article to be plated. The electrode allows current to pass through the article during plating.
All of these devices work well for the purposes they were designed. U.S. Pat. No. 4,294,681 and 4,126,521 have unique characteristics that limit their use to the specific applications taught. U.S. Pat. No. 3,527,679 teaches a much broader application. However, this design has inherent problems: after the rubber mold is used a number times, it becomes weak and damaged. Thus, it has a short life. Although it is an improvement over the individual painting process for masking, it lacks durability.